1. Field of our Invention
Our invention pertains to apparatus for manipulating mechanical heart valve prostheses and in particular to a heart valve prosthesis rotator having a flexible drive shaft.
2. Description of Related Art
Mechanical Heart Valve Prosthesis include ball valves and valves having one, two or more rigid leaflets. One popular valve design for a mechanical heart valve prosthesis includes an annular valve body in which a pair of opposed leaflet occluders are pivotally mounted. The occluders are movable between a closed, mated position, blocking blood flow in an upstream direction and minimizing regurgitation, and an open position, allowing blood flow in a downstream direction. The annular valve body is surrounded by a sewing ring which permits the surgeon to suture the valve in place at the site of an excised valve.
When a valve is placed within the heart, it must be accurately oriented to maximize its function. Particularly in mechanical heart valves, the orientation of the leaflets is critical since their opening and closing pathways may otherwise impinge on the surrounding cardiac walls, the walls of arteries within which the valve is placed, or the residual valvular structures including the tendeae chordae and papillary muscles. This difficulty becomes particularly acute when in the placement of a heart valve in the position of the mitral valve in the heart. When replacing this valve, a surgeon will frequently expose the posterior side of the patient's heart and enter the heart through the wall of the left atrium and sometimes through the right atrium. It is desirable to place the valve accurately within the cramped confines of the heart while leaving room for the surgeon to sew the valve in place.
To aid in the rotation of the heart valve within a sewing ring, heart valve prosthesis rotators have been proposed heretofore. Some of these rotators have bendable metal shafts which can be bent by the surgeon interoperatively, but which will retain their bent shape, requiring significant space for proper manipulation of a heart valve engaged by the rotator. The shafts of some of these rotators are constructed of a shape-memory alloy, which construction allows the shaft to recover its original straight shape upon sterilization. The term "shape-memory alloys" refers to that group of metallic materials that demonstrate the ability to return to same previously defined shape and size when subjected to the appropriate thermal procedure. These materials can be plastically deformed at some relatively low temperature, and upon exposure to higher temperatures, will return their shape prior to the deformation. Rotators containing shape-memory alloy shafts can be easily positioned by bending the shaft to the desired orientation. To return the shaft to its original shape, the shaft is heated (i.e., during the sterilization process) to a temperature above the alloy's transformation temperature.
With the increased use of less invasive cardiac surgical procedures a rotator is needed that can turn a heart valve within a very limited space. To accomplish this, a rotator must have both flexibility and torqueability (i.e. kink resistance). The rotator must have the ability to absorb large amounts of strain energy and release it as the applied strain is released.